1. Field of the Invention
The invention relates to gas turbine combustors and more particularly to a combustor having a catalytic reactor element and a premix chamber for uniform mixture of the air and fuel components prior to entering the catalytic element.
2. Description of the Prior Art
In gas turbine combustors utilizing catalytic reactor elements it is relatively important to maintain the air-fuel mixture entering the catalytic element generally uniform throughout a plane transverse to the direction of flow just prior to the element. Otherwise, with poor mixture, extra lean or extra rich mixtures may enter portions of the catalytic element, where, because of confined internal passages, they are prevented from further mixing and thus the improper mixture ratios can produce smoke, CO, NO.sub.x, unburned hydrocarobons or even result in temperatures that can destroy the catalyst. Thus, it can be seen, without proper premixing, the catalytic element can in fact result in the formation of an undesirable exhaust which it was primarily intended to eliminate.
To avoid this, the air-fuel mixture is caused to premix to a uniform predetermined ratio within which the catalytic element was designed to operate and, in fact, reduces such types of undesirable exhaust components. Such uniform premixing can be accomplished by having a sufficiently long flow path subsequent to the commingling of the air and the fuel to give the two an opportunity to become thoroughly mixed. However, because of the limitations on size and bulk of a commercially feasible gas turbine, the combustion chambers must be kept within acceptable size limitations. Other considerations require the mixing to be done with a relatively low pressure loss to maintain the overall efficiency of the turbine.
Swirling apparatus have been used, however, such devices still permit some stratification of the airfuel mixture such that the mixture is not uniform across the catalyst.